1. School of Materials Science and Engineering
2. Dalian Jiaotong University
3. Dalian 116028
4. P. R. China
5. Department of Optoelectronic Science
6. Harbin Institute of Technology at Weihai
7. Weihai 264209
8. Changchun University of Science and Technology
9. Changchun 130022
10. School of Civil and Environmental Engineering
11. College of Engineering
12. Nanyang Technological University
13. Singapore 639798